Win Forms DataGridView - showing hierarchical parent/child rows

Question

I am trying to construct a datagridview that will show a number of rows with a particular set of fields, but also allow me to show some 'subrows' ie rows that can be expanded below the parent row in question (if that parent row has these children - part of the datasoruce) the only real problem is that the expanded rows will have completely different fields(columns)

is this possible with a standard datagridview in a windows form? I am presuming somehow I would have to shoehorn in a new datagridview in a row of the parent grid.

We do have the Syncfusion suite which includes the gridgroupingcontrol. but after much hair pulling and other pains. I have given up on that completely.

Answer 1

Yes this can be done.

Set a data relation, either in the dataset designer or in code between the two tables using the foreign key - parent key columns.

If in the dataset designer, set the nested property to true. This will then give you child records under each parent row in the datagrid view.

Answer 2

 public class QuestionNode
    {
        public decimal QuestionCode { get; set; }
        public decimal parentQuestionCode { get; set; }        
        public string AssessmentSection { get; set; }
        public string shortName { get; set; }
        public List<QuestionNode> ChildQuestionNode { get; set; }
    }

            CellStyle cs = grdData.Styles.Normal;
            cs.Border.Direction = BorderDirEnum.Vertical;
            cs.TextAlign = TextAlignEnum.LeftCenter;
            cs.WordWrap = false;
            cs = grdData.Styles.Add("Data");
            cs.BackColor = SystemColors.Info;
            cs.ForeColor = SystemColors.InfoText;
            cs = grdData.Styles.Add("SourceNode");
            cs.BackColor = Color.Yellow;
            cs.Font = new Font(grdData.Font, FontStyle.Bold);

            // outline tree
            grdData.Tree.Column = 0;
            grdData.Tree.Style = TreeStyleFlags.Simple;
            grdData.AllowMerging = AllowMergingEnum.Nodes;

            // other
            grdData.AllowResizing = AllowResizingEnum.Columns;
            grdData.SelectionMode = SelectionModeEnum.Cell;



            grdData.SuspendLayout();
            grdData.Rows.Fixed = 1;
            //grdData.DataSource = dt;
            grdData.Cols[0].Visible = false;
            grdData.Cols[1].Visible = false;
            if (_ID == 9)
                grdData[0, 0] = "HCFA-672 Assessment";
            else if (_ID == 10)
                grdData[0, 0] = "HCFA-802 Assessment";

            RcsResidentReporterBL resReportBL = new RcsResidentReporterBL();
            DataTable dt = resReportBL.GetCriteriaQueslkp(_ID, facilityID);

            List<QuestionNode> qtree = new List<QuestionNode>();

            foreach (DataRow dr in dt.Rows)
            {
                QuestionNode parentNode = new QuestionNode();
                parentNode.QuestionCode = Convert.ToDecimal(dr["QuestionCode"]);
                parentNode.AssessmentSection = dr["AssessmentSection"].ToString();
                parentNode.parentQuestionCode =       Convert.ToDecimal(dr["ParentQuestionCode"]);
                parentNode.shortName = dr["ShortName"].ToString();
                var qry = dt.AsEnumerable().Where(x => x.Field<int>("ParentQuestionCode") == parentNode.QuestionCode)
                                            .Select(x => new { QuestionCode = x.Field<int>("QuestionCode"), AssessmentSection = x.Field<string>("AssessmentSection"), ShortName = x.Field<string>("ShortName") }).ToList();
                parentNode.ChildQuestionNode = new List<QuestionNode>();
                parentNode.ChildQuestionNode.Add(parentNode);
                qtree.Add(parentNode);
            }

                Action<QuestionNode> SetChildren = null;
                SetChildren = parent =>
                {
                    parent.ChildQuestionNode = qtree
                        .Where(childItem => childItem.parentQuestionCode == parent.QuestionCode)
                        .ToList();

                    //Recursively call the SetChildren method for each child.
                    parent.ChildQuestionNode
                        .ForEach(SetChildren);
                };

                //Initialize the hierarchical list to root level items
                List<QuestionNode> hierarchicalItems = qtree
                    .Where(rootItem => rootItem.parentQuestionCode == 0)
                    .ToList();

                //Call the SetChildren method to set the children on each root level item.
                hierarchicalItems.ForEach(SetChildren);

                foreach (QuestionNode qst in hierarchicalItems)
                {
                    GetChildren(qst, 0, true, -1);
                }



 private void GetChildren(QuestionNode parentNode, int level, bool useC1Way, int parentrow)
        {

            // add new row for this node
            int row;
            if (useC1Way == true)
            {
                //This is the code by C1
                // add new row for this node
                row = grdData.Rows.Count;
                grdData.Rows.Add();
                grdData[row, 0] = parentNode.AssessmentSection;
                if (parentNode.ChildQuestionNode == null)
                {
                    grdData[row, 1] = "?";
                    grdData.SetCellStyle(row, 1, grdData.Styles["Data"]);
                }

                // make new row a node
                grdData.Rows[row].IsNode = true;
                grdData.Rows[row].Node.Level = level;
            }
            else
            {
                //And this is my different version: at level 0, add a row. At child levels, insert "last child"
                if (level == 0)
                {

                    Row zeile = this.grdData.Rows.Add();
                    zeile.IsNode = true;
                    zeile.Node.Level = 0;

                    grdData[zeile.Index, 0] = parentNode.AssessmentSection;

                    //This also works...
                    //Node nodeGrid = grdData.Rows.AddNode(0);
                    //grdData[nodeGrid.Row.Index, 0] = node.Name;
                }
                else
                {
                    //int row = grdData.Rows.Count;
                    //grdData.Rows.Add();
                    grdData.Rows[parentrow].Node.AddNode(NodeTypeEnum.LastChild, parentNode.AssessmentSection);

                }
                row = grdData.Rows.Count - 1;
            }
            //grdData[row, 0] = node.Name;
            if (parentNode.ChildQuestionNode == null)
            {
                grdData[row, 1] ="?";
                grdData.SetCellStyle(row, 1, grdData.Styles["Data"]);
            }

            // make new row a node
            //grdData.Rows[row].IsNode = true;
            //grdData.Rows[row].Node.Level = level;

            // if this node has children, get them as well
            if (parentNode.ChildQuestionNode != null  && parentNode.ChildQuestionNode.Count > 1)
            {
                // recurse to get children
                foreach (QuestionNode child in parentNode.ChildQuestionNode)
                    GetChildren(child, level + 1, useC1Way, row);
            }
        }

Answer 3

Short answer: No. You need a custom component for this.

There are a lot of good efforts out there on making a hierarchical treeview. Like in the CodeProject article TreeView with Columns or FlexGrid from Component One (paid). I understand you want different fields on the subnodes though, and I'm unsure to what extent these controls support that. I know FlexGrid support some customization of columns for different rows, but it will probably involve quite some manual work - databinding is not well supported.

Finally, you might want to consider if your idea of a customized GridView is the best approach to your problem in the first place. Could a Master-Detail-view be a better approach?

PS: I'm not affiliated with ComponentOne, but I've used FlexGrid in a project.